This new animation shows how close Antarctica is to losing an iceberg the size of Delaware

The giant rift in Antarctica's Larsen C ice shelf, as seen in November 2016.

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John Sonntag/IceBridge/NASA Goddard Space Flight Center

A block of ice about the size of Delaware could break off of
Antarctica "within days," researchers suggest. And a new
animation shows just how close the humongous iceberg is to
calving.

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Antarctica's Larsen C ice shelf - one of the largest such shelves
in the southern continent - began developing the crack in 2010.
That rift lengthened and widened over the years, but has grown
most rapidly since 2016. In early June,
new satellite images showed the rift had split, turned north,
and begun moving toward the Southern Ocean.

Now Adrian
Luckman of Swansea University in the UK, who is closely
monitoring Larsen C with his colleagues, has released a new
animation of the rift's rapid growth.

The images reveal how the rift "jumps" as it
slices through bands of weak ice, slows when it hits denser
ice, and speeds up again when it encounters more weak ice. In the
animation, the ocean is shown in emerald green (top right), the
Larsen C ice shelf is the light blue patch, and the glacier
behind it is white.

It's impossible to say precisely when the rift will snap the ice
off, but Dan McGrath, a scientist with the US Geological Survey,
thinks it won't be long.

"I would expect it to occur quite rapidly, within days or weeks,"
McGrath, who researches Larsen C,
told Reuters on June 1. The ice block makes up about 10% of
Larsen C's total area.

"The rift tip appears also to have turned significantly towards
the ice front, indicating that the time of calving is probably
very close," wrote Luckman and O'Leary, who collaborate on the
Impact of Melt on Ice Shelf Dynamics and Stability project, also
known as Project MIDAS. "There appears to be very little to
prevent the iceberg from breaking away completely."

More recent satellite data, released on June 6 and June 12,
suggests the rift has shown "no significant change ... since May
31", according to Project MIDAS Twitter
account (which is run by O'Leary). He added
that new satellite data wouldn't arrive in until Sunday, June 18.

When the iceberg does shed, it will not significantly raise sea
levels, since it's already sitting in the ocean. But Luckman and
O'Leary said that without the soon-to-calve iceberg, the rest of
Larsen C "will be less stable than it was prior to the rift".

Put another way: There's a slim chance that the entire Larsen C
ice shelf, and an ancient glacier behind it, could later
disintegrate and fall into the sea.

The chaos wouldn't be unprecedented in recorded history. In 2002,
a neighboring ice shelf called Larsen B collapsed and broke up in
the Southern Ocean. If Larsen C and its accompanying glacier
collapse, sea levels might rise by up to four inches.